The present invention generally relates to balloons useful as medical devices, as well as the procedure utilizing the same. More particularly the invention relates to medical or surgical balloons, and to catheter assemblies incorporating them that are useful in dilating blocked vasculature and other body passageways through the intraluminal expansion of the balloon. With the apparatus and method of the present invention, a balloon positioned at the site of the blockage may be inflated and deflated according to a programmed pattern thereby obviating the prolonged total cessation of blood flow to distal sites as in conventional balloon catheter devices.
Angioplasty is one therapeutic approach by which blocked vascular tissue may be opened. In balloon angioplasty, a practitioner typically positions a deflated and collapsed balloon, affixed near or at a distal end of a catheter, at the partially or nearly wholly occluded area of the vessel. The practitioner manually inflates the balloon thereby applying pressure to the intraluminal surface of the vascular blockage. The obstructing material is compressed against the walls of the afflicted vessel and, as is often the case, the vessel wall is stretched and the capsule surrounding the vessel torn. Upon deflating the balloon, an enlarged opening results through which blood may flow freely again. The procedure advantageously obviates the need for surgical methods which expose, incise, remove, replace or bypass the deficient blood vessel.
The conventional approach to balloon angioplasty relies heavily on the practitioner's manual dexterity and experience. To illustrate, the procedure typically requires the practitioner to estimate the rate at which the balloon must be manually expanded. If, for example, the practitioner estimates that the blockage may be particularly responsive to a quick compressive force, the practitioner may expand the balloon at a rapid rate. The procedure requires also the practitioner to estimate the optimal maximum pressure to which the balloon must be manually inflated. Because some stenoses, such as atherosclerotic plaque, are generally compression-resistant, the practitioner may decide to inflate the balloon to a greater maximum pressure level. Additionally, this procedure requires the practitioner to estimate the length of time a given pressure must be maintained in order to effect the proper degree of dilatation. Some tissue may not dilate in response to a quick compression force.
The major drawback associated with the conventional approach to balloon angioplasty is that it is an empirical art, that, because the response to the varying rate, maximum pressure, and length of inflation time is not altogether predictable, produces inconsistent and often times unexpected and potentially dangerous results. For example, if the practitioner inflates the balloon at too rapid of a rate or to too high of a pressure, the balloon and the afflicted vessel may rupture. Inflating the balloon to a moderate pressure level to avoid a rupture may create a different set of problems. Because even a moderately-pressurized balloon typically blocks the flow of blood to areas distal to the treatment site, coronary pressure in the distal region resultingly falls off. In the case of percutaneous transluminary coronary angioplasty, the lack of blood flow past the inflated balloon deprives the heart muscle of oxygen; eschemia results. Patients generally begin to complain of the associated pain after twenty seconds. However, ninety seconds is the maximum amount of time the flow of blood can be completely blocked. At this point, the pain becomes unbearable and the risk of eschemia-related cardiac infarction is extremely high.
Accordingly, prior to the development of the present invention, there was a demand in the art for an apparatus and method by which vascular passageways may be opened in a more controlled and less empirical manner. Specifically, there was a demand for an apparatus and method by which balloon angioplasty may be performed that did not have the associated prolonged stoppage of blood flow to sites distal to the treatment site. For example, by such a preferred apparatus and method the balloon could be inflated and deflated in rapid succession for a period of four minutes--instead of a continuous inflated period of ninety seconds--to allow for intermittent blood flow past the balloon. The present invention fills the demand.
An improved balloon inflation device is provided which includes a drive mechanism by which pump means can be actuated in order to deliver or remove a volume of fluid to or from an angioplasty balloon of a known amount and according to a pre-determined pattern. The actual fluid conditions present in the balloon and the catheter, to one end of which the pump means is attached and to the other general end of which the balloon is attached, are automatically quantified by a monitoring means included with the drive mechanism and communicated to a microprocessor. Besides including sufficient logic to operate the drive mechanism, the microprocessor includes programmed logic by which data regarding the actual fluid conditions developed within the balloon is compared to a set of expected conditions. Deviations from the pre-determined pattern, such as caused by fluid leakage from the catheter and/or angioplasty balloon, are automatically corrected by appropriate orders developed by the microprocessor and communicated to the drive mechanism. Furthermore, the drive mechanism may include logic by which the volume of the balloon and the pressure within it may be compared in order to determine the actual radial change of the balloon. The feature is especially advantageous for compliant balloons.
Accordingly, it is a principal object of the present invention to provide a new apparatus and method with which to perform percutaneous transluminal coronary angioplasty (PTCA), as well as other dilatation procedures.
A further object of the invention is to provide a new apparatus and method by which a balloon included with a PTCA catheter assembly and specifically the balloon's expansion and contraction may be more finely controlled.
Another object of the invention is to provide a new apparatus and method in which the pressure within, and thereby the external dilative force applied by an angioplasty balloon or the like is controlled according to programmed logic.
An additional object is that the control of the expansion and contraction of the angioplasty balloon is provided by programmed logic contained within a microprocessor through control of the drive mechanism of the present invention.
These and other objects, features and advantages of this invention will be more clearly appreciated and understood through a consideration of the following detailed description.